One example of an emerging video compression standard is the Moving Picture Expert's Group (“MPEG”) standard. Within the MPEG standard, video compression is defined both within a given picture, i.e., spatial compression, and between pictures, i.e., temporal compression. Video compression within a picture is accomplished by conversion of the digital image from the time domain to the frequency domain by a discrete cosine transform, quantization, variable length coding, and Huffman coding (both collectively referred to as “run length coding”). Video compression between pictures is accomplished via a process referred to as “motion compensation” in which a motion vector is used to describe the translation of a set of picture elements (pels) from one picture to another.
For MPEG-2 video encoding, FIFOs are often used to capture video data which has been compressed to the MPEG-2 standard, that is digital video data that has been spatially and temporally compressed, as by discrete cosine transformation, quantization, variable length coding, Huffman coding, and motion estimation. In many applications, the FIFOs are unloaded “real time” for transmission of full motion video through a transmission medium. In certain applications, reading of data from the FIFOs may be required only after a predetermined amount of data is loaded into the FIFOs. In other MPEG-2 encoding applications, memory devices instead of FIFOs may be used to capture compressed video data. Some of these devices, such as field memories, do not provide any memory flags which would be useful in reading the memory device when the device is empty or in notifying a host of the memory status.